diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 302ecfb4a6a..b42ecdf2202 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -25,7 +25,7 @@ so we can correct that!
 See [`HACKING_QUICKSTART.md`](docs/HACKING_QUICKSTART.md) for more information
 on how to start working on Servo.
 
-## Pull Request Checklist
+## Pull request checklist
 
 - Branch from the master branch and, if needed, rebase to the current master
   branch before submitting your pull request. If it doesn't merge cleanly with
@@ -49,6 +49,20 @@ on how to start working on Servo.
 
 For specific git instructions, see [GitHub workflow 101](https://github.com/servo/servo/wiki/Github-workflow).
 
+## Running tests in pull requests
+
+When you push to a pull request, GitHub automatically checks that your changes have no compilation, lint, or tidy errors.
+
+To run unit tests or Web Platform Tests against a pull request, add one or more of the labels below to your pull request. If you do not have permission to add labels to your pull request, add a comment on your bug requesting that they be added.
+
+| Label | Effect |
+|---|---|
+| `T-full` | Unit tests: Linux, macOS, Windows<br>Layout tests: Linux, macOS<br>Legacy layout tests: Linux, macOS |
+| `T-linux-wpt-2013` | Unit tests: Linux<br>Legacy layout tests: Linux |
+| `T-linux-wpt-2020` | Unit tests: Linux<br>Layout tests: Linux |
+| `T-macos` | Unit tests: macOS |
+| `T-windows` | Unit tests: Windows |
+
 ## Conduct
 
 Servo Code of Conduct is published at <https://servo.org/coc/>.